1. Field of the Invention
The present invention relates to a motor driving circuit for driving a spindle motor at high efficiency with reduced noise. Such a spindle motor is applied a hard disk drive, optical disk drive, fan and the like.
2. Description of Related Art
A conventional motor driving circuit for driving a three-phase brushless spindle motor is configured such that its commutation control circuit for switching the current-supply pattern of the three-phase output currents does not switch the current-supply pattern suddenly, but softly within certain electrical angle sections an electrical angle section detecting circuit detects. The electrical angle section detecting circuit detects the sections for softly switching the current-supply pattern in response to a signal indicating that the induced voltages of the motor the induced voltage detecting circuit detects cross the motor neutral voltage, and notifies a commutation selecting circuit constituting the commutation control circuit of the sections. The commutation selecting circuit switches the current-supply pattern in response to the detection result of the induced voltage detecting circuit, and generates a control signal corresponding to the current-supply pattern after the switching with reference to the switching sections for softly switching the current-supply pattern.
In response to the control signal, the commutation control circuit gradually varies the PWM duty in the specified sections for switching the current-supply pattern to softly switch the current-supply pattern, thereby reducing the driving noise of the motor produced by the sudden changes in the output currents (see, relevant reference 1).
Relevant reference 1: U.S. Pat. No. 6,242,875 B1, FIGS. 11-19, and the descriptions of the third preferred embodiment in the specification.
With the foregoing configuration, the conventional motor driving circuit has a problem of being unable to reduce the motor driving noise effectively. This is because since it does not control the output currents of the motor directly, the waveforms of the output currents vary with the changes in induced voltage constants and the number of revolutions of the motor.
The present invention is implemented to solve the foregoing problem. It is therefore an object of the present invention to provide a motor driving circuit capable of sharply reducing the driving noise and increasing the driving efficiency of the spindle motor used for the hard disk drive, optical disk drive, fan and the like.
According to a first aspect of the present invention, there is provided a motor driving circuit including current control means for generating current control command signals from the detection result of position detecting means for detecting the position of the rotor of a motor; and current detecting means for detecting the output currents of the motor, for comparing the output currents with the current control command signals, and for controlling output means for outputting the output currents of the motor in response to its comparison result. It offers an advantage of being able to shape the output currents in a sinusoidal waveform and to reduce the motor driving noise.
According to a second aspect of the present invention, there is provided a motor driving circuit including control signal generating means for correcting phases of the detection result of position detecting means for detecting the position of the rotor of a motor with Hall elements; current control means for generating current control command signals in response to the detection result corrected; and current detecting means for detecting the output currents of the motor, for comparing the output currents with the current control command signals, and for controlling output means for outputting the output currents of the motor in response to its comparison result. It offers an advantage of being able to shape the output currents in a sinusoidal waveform and to reduce the motor driving noise.
According to a third aspect of the present invention, there is provided a motor driving circuit including control signal generating means for generating three-phase control signals, each of which corresponds to one of the phases of the three-phase motor, by correcting phases of the detection result of position detecting means for detecting the position of the rotor of a three-phase motor with Hall elements; current control means for generating current control command signals by combining the three-phase control signals; and current detecting means for detecting the output currents of the motor, for comparing the output currents with the current control command signals, and for controlling output means for outputting the output currents of the motor in response to its comparison result. It offers an advantage of being able to shape the output currents in a sinusoidal waveform and to reduce the motor driving noise.